Opening negotiation strategy?

[Michael Cerny]

I'm looking at a SFR in Houston that the seller wants $80/ft for. Comps + rental numbers + rehab mean that $55-60 is a more reasonable estimate of value.

How do you approach the negotiation for this? Do you just throw an offer over the transom? Do you query the listing agent to find out whether the seller has any room to move? When you make the offer, do you put any effort into explaining why you think your number is better?